ThisproposalaimstoelucidatetheroleofD52-mediatedanterogradeendosomaltraffickingduring physiologicalandpathologicalconditionsoftheexocrinepancreas.Acinarcells,theprimarycelltypeofthe exocrinepancreas,areresponsiblefortheregulatedsynthesisandsecretionofinactivedigestiveenzymes (zymogens).Intracellularactivationofzymogensleadstoacinarcelldamageandpancreatitis,anextremely painfulinflammatorydiseaseoftheexocrinepancreaswithlittleornotreatmentoptionsotherthanpalliative care1?3.Acinarcelldamageinitiatestranscriptionalreprogrammingtoaproliferativestem-celllikeprogenitorin aprocesstermedacinartoductalmetaplasia(ADM)4,5.Whilethisresponseisessentialforglandrepair,the progenitorcellsaresusceptibletomalignanttransformationandprogressiontowardpancreaticcancer5.Loss ofanterogradeendosomaltraffickingduringpancreatitishasbeenidentifiedasamajorpathogenicevent leadingtoacinardamageinexvivoacinarcultures6.Additionally,preliminarystudieshaveestablishedastrong linkbetweenthemaintenanceofanterogradeendosomaltraffickingandcontrolofacinarcelldifferentiation;? indicatingthatlossofthispathwayisacriticaleventinthelossofacinarterminaldifferentiationduring pathology.Thisproposalwillexamininghowtheanterogradeendosomalsecretorypathwaycontrolsacinarcell fateinvivousinganacinar-specific,induciblemousemodelofD52deletion.Aim1willassessthe morphologicalandfunctionalconsequenceofacinar-specificD52deletionintheadultmurinepancreas.Aim2 willstudytheeffectofacinar-specificD52deletiononpancreatitisonset,progressionandrecoveryinrodents. Effectswillbeassessedatawholebody,organ,andcellularleveltofullycomprehendthemechanismsatplay. Animalswillbemonitoredforphenotypicchangesingeneralhealth,pancreaticinsufficiency,andacinar damage.Presenceofedema,inflammatorycellinfiltration,andfibrosiswithinthepancreaswillbedetermined toquantifypathology.Aciniwillbeisolatedtoevaluatemorphology,differentiationstatus,secretoryactivity andpolarity,unfoldedproteinresponseactivation,andpresenceofmembranetraffickingpathways.Finally, cellularmarkersofpancreatitiswillbeexamined.Basedonexvivowork,itishypothesizedthatlossofD52- mediatedanterogradeendosomaltraffickingwillinhibitterminaldifferentiationofacinarcells,exacerbating pathologicalconditions.Theroleoftheendosomalsysteminacinardifferentiationisayetunexploredareaof acinarbiology,representingapreviouslyunrecognizedmechanismforpreservingacinarcellfunctionandthe potentialfornewavenuesofpancreatitistreatment.Thecellularandmolecularmechanismsdrivingacinarcell dedifferentiationandredifferentiationduringglandrepairarestillemergingandrepresentacriticalvoidinour understandingofpancreaticdisease.Thisproposalisdesignedtoprovidebasicmechanisticinsightinto terminalacinardifferentiationunderbothphysiologicalandpathologicalconditions,fittingwellwithinthe missionoftheNIHtodiscoverfundamentalknowledgeofhumanhealthanddisease.